Two hundred milligrams of vitamin C may be an appropriate daily
amount for healthy men, according to a new study by the National
Institutes of Health (NIH). The findings are published in the April
16 Proceedings of the National Academy of Sciences.

"Eating five fruits and vegetables a day will easily provide 200
mg," says principal investigator Dr. Mark Levine of the National
Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), a
part of the NIH.

Seven healthy men aged 20 to 26 years old were hospitalized for
4 to 6 months and fed a vitamin C-restricted diet. Reducing the
amount of stored vitamin C in the body ensured accurate
measurements of absorption of the nutrient for daily doses ranging
from 30 mg to 2,500 mg.

Among Levine's findings: at 30 mg, six patients reported feeling
tired and irritable. At 200 mg, plasma had more than 80 percent
maximal concentration of vitamin C and tissues were completely
saturated. Doses of 500 mg and higher were completely excreted in
urine. At 1,000 mg, some volunteers showed potential adverse
effects, such as high levels of oxalate and uric acid in the urine,
which might lead to kidney stones. "It's almost as if we are
programmed to have a certain amount of vitamin C and no more," says
Levine.

The study is the first to measure levels of absorption,
distribution and excretion of vitamin C for multiple doses in
patients who are hospitalized, which ensures accurate dosage and
control of diet. Such a rigorous study provides the kind of data
needed to establish a Recommended Daily Allowance (RDA). The
current RDA for vitamin C, which is determined by the Food and
Nutrition Board of the National Research Council, is 60 mg. That
value is based on the amount of vitamin C needed to prevent a
person from getting scurvy and provide body stores for about 30
days, with a margin of safety.

"It's a great incentive for people to eat more fruits and
vegetables," says Dr. Van Hubbard, director of NIDDK's Division of
Nutrition Research Coordination. He explains that vitamin C
contributes to healing wounds, maintenance of capillaries, bones
and teeth, and absorption of iron. Citrus fruits, strawberries, and
green vegetables such as broccoli are rich in vitamin C.

"There's another message here for doctors," Levine adds. "They
should ask patients who complain of fatigue or irritability what
they eat. If their diet is all fast food, they may be deficient in
vitamin C. It's a good, cheap intervention to first try adding
fruits and vegetables to the diet for a few weeks."

Levine is now studying ideal intake for women. When asked
whether he takes supplements, Levine says, "I used to, but now I
eat my fruits and vegetables."